GEORGETOWN, Del. -- Former pediatrician Melvin Morse sharply controlled and abused his ex-wife's daughter for years, at times suffocating her and forcing her to stand for hours in awkward positions, prosecutors alleged Tuesday at the start of his trial on charges of reckless endangerment and endangering a child's welfare.

The daughter lived in "a household where the defendant was lord and master," Deputy Attorney General Melanie Withers told the jury.

Morse, who lost his Delaware medical credentials after his arrest in August 2012, has pleaded not guilty to the charges.

In Withers' opening statement, the prosecutor said Morse treated the victim - who was 11 when Morse was arrested, and is 12 now - much more harshly than her half-sister, who was Morse's biological child. The victim has a different father.

The sisters "lived very different lives under the same roof," Withers told the jury. The younger daughter "was sent to a private school. She was given plenty of toys to play with, and was never abused physically."

But the victim, Withers said, lived in fear of Melvin Morse. He would punish her nearly every day, Withers said, forcing her to stand in certain positions for hours, or ordering her not to leave her room.

"When his other punishments weren't enough, he would nearly drown her. He called it waterboarding," Withers said.

Other times, Withers said, Morse used his hand to close the girl's nose and mouth. "She would go limp, just to make him think he'd gone too far, and he would stop," the prosecutor said.

Morse's lawyer, Joe Hurley, asked the jury not to jump to conclusions based on the prosecution's witnesses. And in his opening statement, Hurley claimed the daughter and her mother have lied about Morse before in police interviews.

Hurley told the jury they'd hear testimony that the older daughter had recanted earlier allegations that Melvin Morse hit her. And Pauline Morse, he suggested, was only cooperating with prosecutors to be reunited with her daughters, who only see their mother on supervised visits.

"Her role is to dance to the song that is played," he said.

The trial is expected to take two weeks, with testimony from the daughter, Melvin Morse and Pauline Morse.

According to Tuesday's testimony from police and a hospital nurse, the daughter told police she ran away on July 13, 2012, because the night before Melvin Morse had dragged her across a gravel driveway, spanked her and said she would get a severe punishment the next day. The nurse, who examined the child that day, testified she had several bruises and abrasions on her body.

In a videotaped interview with police that day shown to the jury, Melvin Morse said: "It's true, I said, 'Tomorrow you're going to get punished like you've never been punished.' " But, he told police, he did not spank the girl, and had not slapped her once in the past three years, following a social-services probe.

"We don't spank her. I don't do the discipline on her," Morse says in the taped interview. "This doesn't sound like it, but I have a really good relationship with her. We always have breakfast together."